Calea zacatechichi Schltdl. (Compositae) produces anxiolytic- and antidepressant-like effects, and increases the hippocampal activity during REM sleep in rodents.

ETHNOPHARMACOLOGICAL RELEVANCE: Calea zacatechichi is a plant with an extensive popular and ritual use in Mexico. In healthy volunteers, it induces well-being and tranquility senses, and facilitates superficial stages of sleep. However, anxiolytic, and antidepressant-like effects and changes on the sleep-waking stages have not been explored. AIM: To determine anxiolytic and antidepressant-like effects of an aqueous extract of C. zacatechichi (CZ) in rodents and to analyze their effects on hippocampal activity in the rat sleep-waking cycle. MATERIAL AND METHODS: CZ anxiolytic- and antidepressant-like effects were evaluated in several mice and rat behavioral paradigms. CZ effects on temporal distribution of sleep were described, and hippocampus EEG frequency patterns were analyzed during the sleep-waking cycle; absolute and relative powers were analyzed during Rapid Eye Movements (REM) and non-REM sleep stages. CZ chemical analysis was performed by UPLC-ESI-MS. RESULTS: CZ produced specific and robust anxiolytic- and antidepressant-like effects in mice and rats, similar to those of prototypical drugs, at doses ranging from 0.5 to 50 mg/kg. CZ at 100 mg/kg produced visible mild sedative effects in rats, associated with a significant increase in Slow Wave Sleep episodes during a 6 h recording, and enhanced fast frequencies of hippocampus (gamma-band:31-50 Hz) during REM sleep. CONCLUSION: Results could support the well-being and tranquility senses reported by healthy consumers, and to explain the oneiric content during dreams and some improvements in cognitive processes described by consumers. Anxiolytic- and antidepressant-like effects of this species, reported for first time in this study could improve some aspects of mental health.

Beta Oscillations Distinguish Between Two Forms of Mental Imagery While Gamma and Theta Activity Reflects Auditory Attention.

Visual sensory processing of external events decreases when attention is internally oriented toward self-generated thoughts and also differences in attenuation have been shown depending on the thought's modality (visual or auditory thought). The present study aims to assess whether such modulations occurs also in auditory modality. In order to investigate auditory sensory modulations, we compared a passive listening condition with two conditions in which attention was internally oriented as a part of a task; a visual imagery condition and an inner speech condition. EEG signal was recorded from 20 participants while they were exposed to auditory probes during these three conditions. ERP results showed no differences in N1 auditory response comparing the three conditions reflecting maintenance of evoked electrophysiological reactivity for auditory modality. Nonetheless, time-frequency analyses showed that gamma and theta power in frontal regions was higher for passive listening than for internal attentional conditions. Specifically, the reduced amplitude in early gamma and theta band during both inward attention conditions may reflect reduced conscious attention of the current auditory stimulation. Finally, different pattern of beta band activity was observed only during visual imagery which can reflect cross-modal integration between visual and auditory modalities and it can distinguish this form of mental imagery from the inner speech. Taken together, these results showed that attentional suppression mechanisms in auditory modality are different from visual modality during mental imagery processes. Our results about oscillatory activity also confirm the important role of gamma oscillations in auditory processing and the differential neural dynamics underlying the visual and auditory/verbal imagery.

Gamma absolute power reveals activation of motor areas after hand immobilization / Potência absoluta da banda gama revela ativação em áreas motoras após imobilização da mão

OBJECTIVE: To analyze changes in gamma band absolute power in motor cortical areas, before and after a condition of hand immobilization for 48 hours. METHOD: Fifteen healthy volunteers, aged between 20 and 30, were submitted to EEG assessment before and after 48 hours of immobilization of the dominant hand, while performing a motor task triggered by a visual stimulus. A two-way repeated measures ANOVA with two within-group factors (moment x condition), each one with two levels (before vs. after visual stimuli; before vs. after 48-hour HI, respectively) was used to test for changes in beta band absolute power. RESULTS: Statistical analysis revealed that hand immobilization caused changes in cortical areas. A significant increase in gamma band absolute power was found after hand immobilization at electrodes F3 (p = 0.001) at F4 (p = 0.001) and at Fz (p = 0.001), at C3 (p = 0.001), C4 (p = 0.001) and Cz (p = 0.001). CONCLUSION: These results reveal that oscillations of the gamma band can be a cortical strategy to solve the effect of less activation due to movement restriction. Knowledge of the functioning of motor cortical areas after a condition of immobilization can lead to more effective strategies in rehabilitation.

OBJETIVO: O objetivo deste estudo foi analisar mudanças na potência absoluta da banda gamma em áreas corticais motoras, antes e depois de uma condição de imobilização da mão por 48 horas. MÉTODO: Quinze voluntários saudáveis, com idades entre 20 e 30 anos, foram submetidos a avaliação eletroencefalográfica antes e depois da imobilização, durante a execução de uma tarefa motora desencadeada por um estímulo visual. Uma análise de variância com dois fatores (ANOVA two-way) foi empregada para investigar o fator momento (antes e depois do estímulo visual) e o fator condição (antes e depois da imobilização). RESULTADOS: Um aumento significativo na potencia absoluta da banda gamma foi encontrado após imobilização da mão nos elétrodos (ou derivações) F3, F4, FZ, C3, C4 e Cz. CONCLUSÃO: Estes resultados revelam que as oscilações na banda gama podem ser uma estratégia cortical para resolver o efeito de menor ativação devido à restrição de movimento. Um melhor conhecimento do funcionamento de áreas corticais motoras após uma condição de imobilização pode orientar estratégias mais eficazes na reabilitação.

Gamma band activity in the reticular activating system.

This review considers recent evidence showing that cells in three regions of the reticular activating system (RAS) exhibit gamma band activity, and describes the mechanisms behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus (PPN), intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD) all fire in the beta/gamma band range when maximally activated, but no higher. The mechanisms behind this ceiling effect have been recently elucidated. We describe recent findings showing that every cell in the PPN have high-threshold, voltage-dependent P/Q-type calcium channels that are essential, while N-type calcium channels are permissive, to gamma band activity. Every cell in the Pf also showed that P/Q-type and N-type calcium channels are responsible for this activity. On the other hand, every SubCD cell exhibited sodium-dependent subthreshold oscillations. A novel mechanism for sleep-wake control based on well-known transmitter interactions, electrical coupling, and gamma band activity is described. The data presented here on inherent gamma band activity demonstrates the global nature of sleep-wake oscillation that is orchestrated by brainstem-thalamic mechanism, and questions the undue importance given to the hypothalamus for regulation of sleep-wakefulness. The discovery of gamma band activity in the RAS follows recent reports of such activity in other subcortical regions like the hippocampus and cerebellum. We hypothesize that, rather than participating in the temporal binding of sensory events as seen in the cortex, gamma band activity manifested in the RAS may help stabilize coherence related to arousal, providing a stable activation state during waking and paradoxical sleep. Most of our thoughts and actions are driven by pre-conscious processes. We speculate that continuous sensory input will induce gamma band activity in the RAS that could participate in the processes of pre-conscious awareness, and provide the essential stream of information for the formulation of many of our actions.